1. Field of the Invention
The present invention relates generally to a mobile communication system, and in particular, to a method for concurrently providing a voice service and a packet service.
2. Description of the Related Art
In general, a CDMA (Code Division Multiple Access) mobile communication system cannot concurrently provide two difference services in an active state. That is, an existing mobile communication system provides only one of the voice service and the packet service, and rejects a newly requested service, which is different from the currently provided service.
FIG. 1 illustrates the stricture of a common mobile communication system. More specifically, FIG. 1 illustrates a reference model of a 3G IOS (3rd Generation Interoperability Specifications) for a digital air interface between a mobile switching center (MSC) and a base station (BS), and between the base station and a mobile station (MS).
Referring to FIG. 1, the mobile communication system includes a mobile switching center (MSC) 10, base stations (BS) 30 and 40 and a packet data service node or network (PDSN) 60. An interworking function (IWF) block 20 is connected to the mobile switching center 10, and a packet control function (PCF) block 50 is interconnected between the base station 30 and the PDSN 60. The mobile switching center 10 includes a call control and mobility management block 12 and a switch function block 14. The base station 30 is a source base station and the base station 40 is a target base station. The base stations 30 and 40 include base station controllers (BSCs) 32 and 42, and base station transceiver subsystem (BTSs) 34 and 44, respectively. The base station controller 32 includes an SDU (Service Data Unit) function block. The base station transceiver subsystems 34 and 44 are wirelessly connected to the mobile stations (not shown). The mobile stations are connected to the mobile switching center 10 via the base station 30 to be provided with the voice service, and connected to the PDSN 60 via the base station 30 to be provided with the packet service.
Signaling data between the mobile switching center 10 and the base station controller 32 is defined as an A1 interface, and user data (or traffic) therebetween is defined as A2/A5 (circuit data only) interfaces. An A3 interface is for a soft/softer handoff between the base stations, and is defined to attach signaling data and user data to a frame selection function of the target base station 40 and the source base station 30. An A7 interface is also for the soft/softer handoff between the base stations, and is defined for the signaling data between the target base station 40 and the source base station 30. A8/A9 interfaces are used to transmit user data and signaling data between the base station 30 and the PCF block 50, respectively. A10 and A11 interfaces are used to transmit user data and signaling data between the PCF block 50 and the PDSN 60, respectively.
In the CDMA system of FIG. 1, wired communication links between the base stations 30 and 40, and between the base station 30 and the mobile switching center 10 include a forward link for transmitting signals from the mobile switching center 10 to the base station 30, a reverse link for transmitting signals from the base station 30 to the mobile switching center 10, and a link between the base station 30 and the base station 40. A mobile station (not shown) connected to the base station transceiver subsystem 34 in the base station 30 is connected to the mobile switching center 10 via the base station 30 to be provided with the voice service, and connected to the PDSN 60 via the base station 30 to be provided with the packet service.
FIG. 2 illustrates a procedure for managing a new service requested while providing an existing (or current) service in the conventional mobile communication system. This procedure is performed in the mobile switching center 10 of the mobile communication system.
Referring to FIG. 2, upon receipt of a new service request, the mobile switching center 10 of FIG. 1 receives the new service request in step S10, and determines in step S11 whether an existing service (or a presently connected service) is connected to a receiving/origination-requested mobile station. If it is determined that the existing service is not connected to the receiving/origination-requested mobile station, the mobile switching center 10 connects the newly requested service to the receiving/origination-requested mobile station in step S12.
Otherwise, if it is determined that the existing service is connected to the receiving/origination-requested mobile station, the mobile switching center 10 determines in step S13 whether the presently connected service is the packet service or not. If the presently connected service is the packet service, the mobile switching center 10 determines in step S14 whether the packet service is in a dormant state. If the packet service is in the dormant state, the mobile switching center 10 proceeds to step S12 and connects the newly requested service to the receiving/origination-requested mobile station.
If the presently connected service is not the packet service in step S13, i.e., if the presently connected service is the voice service or an emergency call service, the mobile switching center 10 proceeds to step S15. The mobile switching center 10 also proceeds to step S15, when the presently connected service is the packet service and the packet service is not in the dormant state in step S14 but in an active state. In step S15, the mobile switching center 10 refuses the newly requested service.
FIG. 3 illustrates a procedure for clearing a presently provided service in the conventional mobile communication system. This procedure is also performed in the mobile switching center 10 of FIG. 1.
Referring to FIG. 3, upon receipt of a service clear (or release) request from an external network (not shown) via the base station 30 or the IWF block 20 of FIG. 1 in step S20, the mobile switching center 10 determines the clear-requested service (i.e., the service to be cleared) and the associated mobile station in step S21. Thereafter, in step S22, the mobile switching center 10 sends a clear command message to the base station 30 (or 40) to clear the service of the corresponding mobile station. Upon failure to receive a clear complete message from the base station 30 within a predetermined time, the mobile switching center 10 repeats to sending a clear command message in step S22. Upon receipt of the clear complete message from the base station 30 in step S24, the mobile switching center 10 clears the service for the corresponding mobile station. That is, in step S24, the mobile switching center 10 clears entire information (e.g., service option and temporary user location information) related to the wire connection and the service connected to the corresponding mobile station.
Accordingly, if the existing service is the packet service and the packet service is in the dormant state, the conventional mobile communication system can provide the newly requested service such as the voice service. However, if the existing service is the activated packet service or the voice service, the conventional mobile communication system cannot provide the newly requested service.